SQLite Exercise: Get the average salary for all departments employing more than 10 employees
Write a query to get the average salary for all departments employing more than 10 employees.
Sample table : employees
+-------------+-------------+-------------+----------+--------------------+------------+------------+----------+----------------+------------+---------------+ | EMPLOYEE_ID | FIRST_NAME | LAST_NAME | EMAIL | PHONE_NUMBER | HIRE_DATE | JOB_ID | SALARY | COMMISSION_PCT | MANAGER_ID | DEPARTMENT_ID | +-------------+-------------+-------------+----------+--------------------+------------+------------+----------+----------------+------------+---------------+ | 100 | Steven | King | SKING | 515.123.4567 | 1987-06-17 | AD_PRES | 24000.00 | 0.00 | 0 | 90 | | 101 | Neena | Kochhar | NKOCHHAR | 515.123.4568 | 1987-06-18 | AD_VP | 17000.00 | 0.00 | 100 | 90 | | 102 | Lex | De Haan | LDEHAAN | 515.123.4569 | 1987-06-19 | AD_VP | 17000.00 | 0.00 | 100 | 90 | | 103 | Alexander | Hunold | AHUNOLD | 590.423.4567 | 1987-06-20 | IT_PROG | 9000.00 | 0.00 | 102 | 60 | | 104 | Bruce | Ernst | BERNST | 590.423.4568 | 1987-06-21 | IT_PROG | 6000.00 | 0.00 | 103 | 60 | | 105 | David | Austin | DAUSTIN | 590.423.4569 | 1987-06-22 | IT_PROG | 4800.00 | 0.00 | 103 | 60 | | 106 | Valli | Pataballa | VPATABAL | 590.423.4560 | 1987-06-23 | IT_PROG | 4800.00 | 0.00 | 103 | 60 | | 107 | Diana | Lorentz | DLORENTZ | 590.423.5567 | 1987-06-24 | IT_PROG | 4200.00 | 0.00 | 103 | 60 | | 108 | Nancy | Greenberg | NGREENBE | 515.124.4569 | 1987-06-25 | FI_MGR | 12000.00 | 0.00 | 101 | 100 | | 109 | Daniel | Faviet | DFAVIET | 515.124.4169 | 1987-06-26 | FI_ACCOUNT | 9000.00 | 0.00 | 108 | 100 | ........... | 206 | William | Gietz | WGIETZ | 515.123.8181 | 1987-10-01 | AC_ACCOUNT | 8300.00 | 0.00 | 205 | 110 | +-------------+-------------+-------------+----------+--------------------+------------+------------+----------+----------------+------------+---------------+
SQLite Code:
-- Selecting the "job_id" and calculating the average salary and count of employees for each department
SELECT job_id, AVG(salary), COUNT(*)
-- Specifying the table from which to retrieve the data, in this case, "employees"
FROM employees
-- Grouping the results by the "department_id" column
GROUP BY department_id
-- Filtering the grouped results to include only those with a count of employees greater than 10
HAVING COUNT(*) > 10;
Output:
job_id AVG(salary) COUNT(*) ---------- ---------------- ---------- SH_CLERK 3475.55555555556 45 SA_REP 8955.88235294118 34
Explanation:
The above SQLite query retrieves the "job_id" and calculates the average salary and count of employees for each department from the "employees" table. The results are grouped by the "department_id" column, and only departments with a count of employees greater than 10 are included in the final result set.
Here's a brief explanation of each part of SQLite code:
- SELECT clause:
- It selects the "job_id" column.
- It calculates the average salary for each department using the AVG function.
- It counts the number of employees in each department using the COUNT(*) function.
- FROM clause:
- Specifies the table from which to retrieve the data, in this case, the "employees" table.
- GROUP BY clause:
- Groups the results by the "department_id" column. This means that the average salary and count of employees are calculated separately for each unique department.
- HAVING clause:
- Filters the grouped results to include only those groups (departments) where the count of employees is greater than 10.
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Model Database
Structure of 'hr' database :
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